XFS sunit/swidth for raid10
Hi,
How does one determine the XFS sunit and swidth sizes for a software raid10 with 3 copies?
Thanks
Peter
Quoted 3 lines · Peter Rabbitson
Hi,
How does one determine the XFS sunit and swidth sizes for a software raid10 with 3 copies?
mkfs.xfs uses the GET_ARRAY_INFO ioctl to get the data it needs from software raid and select an appropriate sunit/swidth...
although i'm not sure i agree entirely with its choice for raid10:
*sunit = md.chunk_size >> 9;
*swidth = *sunit * md.raid_disks;i'd think it would depend on the layout of the raid10 (near, far, offset)... for near2 on 4 disks i'd expect swidth to be only 2*sunit... but for far2 on 4 disks i'd expect 4*sunit... but i'm not sure. it probably doesn't matter.
-dean
Quoted 9 lines · dean gaudet
Quoted 3 lines · Peter Rabbitson
Hi,
How does one determine the XFS sunit and swidth sizes for a software raid10 with 3 copies?mkfs.xfs uses the
GET_ARRAY_INFOioctl to get the data it needs from software raid and select an appropriate sunit/swidth...although i'm not sure i agree entirely with its choice for raid10:
So do I, especially as it makes no checks for the amount of copies (3 in my case, not 2).
Quoted 1 line
it probably doesn't matter.
This was essentially my question. For an array -pf3 -c1024 I get swidth = 4 * sunit = 4MiB. Is it about right and does it matter at all?
Quoted 13 lines · Peter Rabbitson
Quoted 11 lines · dean gaudet
Quoted 4 lines · Peter Rabbitson
Hi,
How does one determine the XFS sunit and swidth sizes for a software raid10
with 3 copies?mkfs.xfs uses the
GET_ARRAY_INFOioctl to get the data it needs from software raid and select an appropriate sunit/swidth...although i'm not sure i agree entirely with its choice for raid10:
Quoted 7 lines
So do I, especially as it makes no checks for the amount of copies (3 in my case, not 2).
Quoted 1 line
it probably doesn't matter.
This was essentially my question. For an array -pf3 -c1024 I get swidth = 4 * sunit = 4MiB. Is it about right and does it matter at all?
how many drives?
-dean
Quoted 13 lines · dean gaudet
Quoted 11 lines · Peter Rabbitson
Quoted 10 lines · dean gaudet
Quoted 4 lines · Peter Rabbitson
Hi,
How does one determine the XFS sunit and swidth sizes for a software raid10
with 3 copies?mkfs.xfs uses the
GET_ARRAY_INFOioctl to get the data it needs from software raid and select an appropriate sunit/swidth...although i'm not sure i agree entirely with its choice for raid10:
Quoted 9 lines
Quoted 6 lines
So do I, especially as it makes no checks for the amount of copies (3 in my case, not 2).
Quoted 1 line
it probably doesn't matter.
This was essentially my question. For an array -pf3 -c1024 I get swidth = 4 * sunit = 4MiB. Is it about right and does it matter at all?
how many drives?
Sorry. 4 drives, 3 far copies (so any 2 drives can fail), 1M chunk.
Quoted 19 lines · Peter Rabbitson
Quoted 18 lines · dean gaudet
Quoted 16 lines · Peter Rabbitson
Quoted 10 lines · dean gaudet
Quoted 4 lines · Peter Rabbitson
Hi,
How does one determine the XFS sunit and swidth sizes for a software raid10
with 3 copies?mkfs.xfs uses the
GET_ARRAY_INFOioctl to get the data it needs from software raid and select an appropriate sunit/swidth...although i'm not sure i agree entirely with its choice for raid10:
So do I, especially as it makes no checks for the amount of copies (3 in my
case, not 2).Quoted 1 line
it probably doesn't matter.
Quoted 8 lines
Quoted 6 lines
Quoted 3 lines
This was essentially my question. For an array -pf3 -c1024 I get swidth = 4 *
sunit = 4MiB. Is it about right and does it matter at all?how many drives?
Sorry. 4 drives, 3 far copies (so any 2 drives can fail), 1M chunk.
my mind continues to be blown by linux raid10.
so that's like raid1 on 4 disks except the copies are offset by 1/4th of the disk?
i think swidth = 4*sunit is the right config then -- 'cause a read of 4MiB will stride all 4 disks...
-dean